DaS Stacked Turbines.
The compressed air pumped into the bottom tank forces the water to the tank on top of the stack. This leaves the bottom tank empty of water and full of compressed air which then escapes to the water filled tank above it.
The compressed air moving up into the second tank then forces its water out and down through a 82% efficient turbine and down into the bottom tank. The compressed air now filling the second tank moves up into the third tank forcing its water out and down through a 82% efficient turbine into the second tank. The compressed air now filling the third tank moves up into the fourth tank forcing its water out and down through a 82% efficient turbine into the third tank and so on till reaching the top tank. The compressed air left in the top tank after forcing its water into the tank below then is released to the atmosphere.
The water restrictor in the line going from the bottom tank direct to the top tank is there to ensure the compressed air does not follow that route.
There is no limit to the number of turbines that can be stacked this way, however two turbines are kept solely for driving and air compressor which inserts a new compressed air bubble into the bottom tank each time the prior compressed air bubble reaches the top tank.
The attached shows workings where the bottom tank has just filled the top prior empty tank.
Sorry about the size of the Blueprint but I had to draw sideways to fit on the page then rotate vertically.
Modify button not working.
Correct attachment.